In recent years, a chemical reaction and a separation system using ultra-fine processing technology which is called a micro reactor or a micro analysis system have been developed. Application of such a chemical reaction and a separation system to analysis and synthesis of a nucleic acid, protein, and the like, rapid analysis of traces of chemical compounds, and high throughput screening of medical supplies and drugs on a microchip with a fine flow channel is expected.
Generally, a microchip with microchannels is prepared by bonding two molded articles, at least one of the molded articles having micropits.
For example, Patent Document 1 discloses a technology of bonding a molded article made from a specific cyclic olefin resin with a molded article made from another resin using an adhesive by applying plasma to the surface of the former molded article before bonding.
However, when the method disclosed in this document is used, the adhesive may ooze from the interface and may pollute microchannels of a microchip and the like.
Patent Document 2 discloses a method of bonding a microchip body having microchannels on the surface with a lid having a flat surface adhering securely to the microchip body by superposing the microchip body on the lid and heating under pressure to cause the resin to become fused.
However, since the method disclosed in this document causes a resin to become fused by heating under pressure, flatness of the interface may be impaired and the microchannels may lose their uniform shape or may be closed due to deformation of the resin.
Patent Document 3 discloses a method of bonding a first microchip substrate having a microchannel provided on its surface and a second microchip substrate having a surface brought closely into contact with that surface with the microchannel of the first microchip substrate by ultrasonic welding.
However, since the method uses ultrasonic vibration, microchips may not be sufficiently fused or are bonded only inadequately depending on the materials or shape of the objects to be bonded.
Patent Document 4 discloses a method of bonding a first microchip substrate having a microchannel provided on its surface and a second microchip substrate having a surface closely brought into contact with that surface with the microchannel of the first microchip substrate by laser welding.
However, since laser beams can be applied only to spots, the method exhibits low productivity when a large area is bonded. It is difficult to apply the method to a material which does not absorb laser beams such as a polymer containing an alicyclic structure. If applied to such a material, the bonding strength is insufficient.
Patent Document 5 discloses a method of bonding a microchip body having microchannels on its surface with a lid having a flat surface adhering securely to the microchip body by coating the area having no microchannels on the surface of the microchip body with an organic solvent, superposing the microchip body on the lid, and bonding the resin by fusing.
However, since the method disclosed in this document causes a resin to become fused by dissolving the interface using an organic solvent, flatness of the interface may be impaired and the microchannels may lose their uniform shape or may be closed due to deformation of the resin.    Patent Document 1: JP-A-3-95235    Patent Document 2: JP-A-2005-77218    Patent Document 3: JP-A-2005-77239    Patent Document 4: JP-A-2005-74796    Patent Document 5: JP-A-2005-80569